The invention relates to a piezoactive motor equipped with one or more stator modules designed to vibrate to cause relative movement of a driven part over a large travel according to a dynamic operating mode, and possibly step by step operation by means of drive means by friction, said stator modules, by deforming, in addition enabling fine positioning of the driven part according to a direct actuator operating mode, each stator module comprising at least:
one pair of colinearly arranged piezoactive actuators electrically excited so as to deform and produce small longitudinal movements, PA1 a mechanical coupling element to which the movements of the two actuators are applied, said element being formed by a ring shaped as a shell and made of a deformable flexible material, surrounding each pair of actuators by fixing at two opposite points. PA1 each stator module is independent from the others, is free to vibrate, and is only fixed to other parts by flexible links performing decoupling in vibration, PA1 each stator module comprises in addition a central countermass playing the role of inertia, inserted without clearance inside the shells between the actuators, PA1 the mass ratio between the countermass and shell is chosen such that in vibration, the longitudinal deformations of the internal actuators generate a movement of the shell, of non-negligible amplitude with respect to that of the countermass, and preferably that the translation mode of the shell and the flexion mode of the shell are tuned in frequency in order to obtain a good efficiency. PA1 a first type of deformation, called translational deformation, is obtained when said piezoactive actuators are deformed longitudinally in opposition producing a tangential movement of the peaks of the shell relatively to the counter-mass. PA1 a second type of deformation, called flexional deformation, is obtained when said piezoactive actuators are deformed longitudinally in identical manner producing a flexion of the shell, the countermass remaining immobile in the centre. Operation in this manner results in a normal movement of the peaks of the shell. PA1 a first pair of piezoactive actuators placed colinearly on each side of the countermass, PA1 a second pair of piezoactive actuators arranged colinearly on each side of the countermass and orthogonally to the first pair, PA1 the shell comprising four branches in the form of semi-ellipses surrounding said actuators, so as to generate at its peak movements in two planes perpendicular to one another.